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CENTRALIZER DEVICE AND METHOD FOR DEPLOYMENT OF A BORE HOLE COMPONENT IN A
BOREHOLE

Abstract

A centralizer device for center positioning of a bore hole component (90,
91) in a bore hole and a method for deploying such a centralizer are
described. The centralizer device (100) is prepared to have two possible
different states, one state being a locked state for improved deployment
and another state being a released state for centring. The transition
from the locked state to the released state is performed by introducing a
pill of bore fluid having a pH-value outside range of pH-values of bore
fluid in a well. The pill of bore fluid dissolves pH-soluble material in
the centralizer device.

1. A centralizer device (100) for center positioning of a bore hole
component (90, 91) in a bore hole, said centralizer device (100) having
two possible different states, one locked state and one released state;
said centralizer device (100) comprising one outer sleeve (10) comprising
ribs and one inner sleeve (20), said inner sleeve (20) being fastened to
a bore hole component (90, 91); characterized by: a lock spring (51)
being pre-tensioned so that it clings to a release spring (52); said
release spring (52) being pre-tensioned with an opposite tension
exceeding the tension of the lock spring (51); wherein, in the locked
state of the centralizer device (100), the outer sleeve (10) and the
inner sleeve (20) are locked to each other, so that longitudinal movement
between the outer sleeve (10) and the inner sleeve (20) is prevented,
wherein the lock spring (51) is positioned both in an outer sleeve latch
groove (70) and in an inner sleeve latch groove (25), and the ribs are
pre-tensioned with outward strain; said release spring (52) being
squeezed toward the inner sleeve (20) by a snap ribbon (30); and in the
released state of the centralizer device (100): the outer sleeve (10) and
the inner sleeve (20) are released from each other, so that longitudinal
movement between the outer sleeve (10) and the inner sleeve (20) is
enabled wherein the lock spring (51) is positioned completely in the
outer sleeve latch groove (10) resulting in said pre-tensioned ribs
applying pressure against a wall of the bore hole; and said release
spring (52) is released and the lock spring (51) as a consequence is
positioned so that it is completely inside the outer sleeve latch groove
(25), said snap ribbon (30) having a locked and a released states, each
such snap ribbon state corresponding to a state of the centralizer
device, wherein in the locked state said snap ribbon (30) comprises one
or more snap-ribbon units (35) connected to each other, said snap-ribbon
unit (35) comprising: a male snap-part (31); a female snap-part (32); and
pH-soluble material (60) positioned between the male snap-part (31) and
the female snap-part (32) locking the male snap-part (31) and the female
snap-part (32) together on a first end of the male snap-part (31) and a
first end of female snap-part (32), said pH-soluble material (60) being
soluble in an environment having a specified pH-value, said snap ribbon
(30), connected with an opposite end of a male snap-part (31) joined to
an opposite end of a female snap-part (32) and deployed in the inner
sleeve latch groove (3) having a length squeezing said release spring
towards the inner sleeve (20) resulting in the lock spring (51) locking
the outer sleeve (10) to the inner sleeve (20); and in the released state
of the snap ribbon (30), said pH-soluble material (60) positioned between
the male snap-part (31) and the female snap-part (32) is dissolved and
locking of the snap ribbon units to each other is stopped, and said
squeezing of the release spring by the snap ribbon is stopped, resulting
in the release spring (52) being released and the lock spring (51) being
pressed inside the outer sleeve (10), the sleeves (10, 20) being released
from each other enabling the ribs pushing against the bore hole wall and
centralizing the centralizing device (100) in the borehole, the
transition from the locked state to the released state being initiated by
subjecting the pH-soluble material (60) to a pH value selected to cause
dissolving the pH-soluble material (60).

2. The centralizer device (100) according to claim 1, wherein said
pH-soluble material (60) is soluble in an environment with a pH-value
outside the range 9.0 to 9.5.

3. The centralizer device (100) according to one of claim 1 wherein said
pH-soluble material (60) soluble in an environment with a pH-value
outside the range 7.0 to 11.0.

4. The centralizer device (100) according to one of claim 1, wherein the
bore hole component (90) comprises a casing (91).

5. The centralizer device (100) according to one of claim 1, further
characterized in that the bore hole component (90) comprises a foundation
plug.

6. A method for deploying of a centralizer device (100), characterized
by: fastening one side of a centralizer device (100) to a bore hole
component (90, 91); deploying the bore hole component (90, 91) together
with the centralizer device (100) in a bore hole; pumping bore fluid
having a pH-value of between 7.0 and 11.0 into the bore hole component
(90, 91) and further into an annulus between the bore hole component (90,
91) and the bore hole; pumping a pill of bore fluid, having a pH-value
outside the range of pH-values between 7.0 and 11.0, thereby initiating
moving the centralizer device from a locked state to a released state so
that the bore hole component (90, 91) is centered inside the bore hole;
and cementing the bore hole component (90, 91).

9. The method according to one of claim 6, wherein the bore fluid has a
pH-value between 9.0 to 9.5.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation of International Application No.
PCT/NO2015/050119 filed on Jun. 26, 2015. The foregoing application
claims priority from Norwegian Patent Application No. 20140848 filed on
Jul. 2, 2014. Both the foregoing applications are incorporated herein by
reference in their entirely.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

[0003] Not Applicable.

BACKGROUND

[0004] The present disclosure is generally related to a centralizer device
and a method for deploying a bore hole component in a borehole. More
specifically, the disclosure relates to a centralizer device that is
caused to be released when the centralizer device is deployed in a
desired position in a borehole, wherein the centralizer device has a
trigger that secures a center positioning of the bore hole component
inside the borehole.

[0005] When a well for production of hydrocarbons such as oil and gas is
to be constructed, a bore hole is in the first place drilled and is
afterwards typically equipped with a casing in the form of a steel pipe.
Cement is pumped into the pipe from the inside top of the steel pipe.
When the cement reaches the bottom of the borehole, the cement is
squeezed between the bore hole and the outside of the pipe. One important
measure of the quality of the well construction is the degree to which
the steel pipe is centred in the bore hole after the cement has hardened.
This measure is often called standoff. A standoff of 100% specifies that
the steel lining is positioned exactly in the center of the bore hole and
that the cement is distributed with a uniform thickness in the annular
space between the bore hole and the exterior of the pipe. If the steel
pipe is positioned so as to touch the bore hole, the standoff is 0% at
this position. Previously, the American Petroleum Institute, Washington,
D.C., (API) specified a minimum standoff of 67%. Some oil and gas
exploration and productions companies, such as Statoil ASA, require a
standoff minimum of 70%. (Ref.: Statoil ASA Technical Requirements:
TR3519 "2.3.2 Centralization".) In order to ensure controlled standoff,
centralizer devices are used. Centralizer devices are devices such as,
e.g., a simple bow-spring centralizer device that is described at the
Uniform Resource Locator (URL) below:

[0007] Centralizer devices are positioned outside the pipe in a bore hole.
Centralizer devices are positioned at an axial distance from each other
that is so short, after hardening of the cement, that the pipe satisfies
the requirements for standoff along the total length of the pipe. Bore
holes that are curved or are horizontal will normally require that the
axial distance between centralizers is shorter to compensate for
increased load and tension in transverse direction to the longitudinal
axis of the bore hole. The required axial distance between centralizer
devices also depends on the respective diameters of the casing and bore
hole. Centralizer devices are placed around a section of a casing when it
is about to be lowered down in a bore hole. The centralizer device is
often fastened directly to the casing and slides into the bore hole
together with the section of the casing. Casings may keep standoff by
centralizer springs in a centralizer device and more or less controlled
strain between the outside of the casing and the wall of the bore hole.
While the casing glides inwards, friction will naturally occur between
said springs and the wall of the bore hole. A large friction may result
in problems in deploying the casing. One may also experience that the
centralizer device gets stuck or gets damaged so that the deployment is
prevented or that the standoff becomes less than desired. This represents
a trade-off between two contradicting requirements, on one side the
centralizer device should be easy to deploy without incurring larger
friction force than necessary, while on the other side should be standing
as fixated as practically possible when the concrete flows downwards
inside the casing and upwards on the outside of the casing and through
all orifices of the centralizer devices. With unnecessary large friction
forces, an increased risk of the centralizer device getting stuck and/or
getting deformed or maybe destroyed may be experienced. This may result
in the current requirements for standoff may get difficult to achieve.

[0008] When the casing is cast in cement, the cement inside the casing is
normally drilled and what remains is a casing fixed by casting between
the casing and the bore hole which is a good basis for further
preparations for producing hydro carbon.

[0009] U.S. Patent Application Publication No. 2010/0078173 discloses a
temperature controlled trigger device with which, e.g., a centralizer
device may be deployed into a bore hole while it is fastened to a section
of a casing. When the casing arrives at its longitudinal position, the
centralizer device can be activated to spread out springs 12 that
initially are placed along the casing and in this way do not spread out
the springs 12 against the wall of the bore hole and create friction and
other related problems. In said '173 publication, a so called memory
alloy or SMA ["Shape Memory Alloy"] which is used for activation of a
mechanism. SMA is a sort of metal alloy which is known to be deformable
and to keep its deformed structure in a low temperature phase (in which
the metal has a martensitic structure) and will thereafter resume its
prior shape when it is brought into its high temperature phase/memory
phase (in which the metal has an austenitic structure). The disclosed
centralizer solves the problems with friction in the deployment phase in
that the centralizer device in the first phase gets deformed to an
appearance with a small outer diameter. When a casing having such a
centralizer device is deployed down into a bore hole to where it is
intended, the temperature thereafter has to be increased until it reaches
the necessary temperature for the centralizer device mechanism to regain
its high temperature phase resulting in the springs 12 of the centralizer
device pressing against the wall of the bore hole. For this type of
centralizer, the trigger temperature of the memory alloy must agree with
the temperature relations in the particular bore hole. It is a problem
that the trigger device is trigged at a temperature that is defined by
the memory alloy and is difficult to adjust. The timing must also be
sufficiently controllable in order to ensure that a practical method can
be established to cause the trigger device to trigger when the casing is
deployed at the correct place in the bore hole. The '173 publication also
describes the possibility to lower the temperature in order for the
memory alloy to keep its martensitic structure for a longer period in a
deep bore hole. In this way such as centralizer may also be used for deep
bore holes in which the temperature otherwise would cause triggering
before the casing had reached the planned position. On the other hand,
this would incur large costs.

[0010] U.S. Pat. No. 3,196,951 describes a centralizer with ribs formed as
wires. These wires are separate parts that are to be installed on the
centralizer before the entire assembly is slid onto a housing and the
wires are fixed on the housing by stop collars 15, 16 and snap rings 17.
When deploying the centralizer described in the '951 patent in a bore
hole, the centralizer operates as an ordinary passive centralizer without
means for reducing the mechanical resistance or improving the final
centralization of the housing or other bore hole component.

SUMMARY

[0011] A centralizer device according to various aspects of the present
disclosure provides a device and a method to ensure a robust and suitable
deployment of a casing in a subsurface well. This regards not the least
in horizontal wells, but also in vertical wells, sloping wells and parts
of wells. Such centralizing may be obtained according to the present
disclosure by means of a centralizer device that is arranged to possess
the ability to be in at least two states in which the outer diameter of
the centralizer, or the pressure against a wall in which it is deployed,
are different. A locked state involves less friction than when using an
ordinary centralizer device by involving less pressure between the
centralizer device and the surrounding wall of a bore hole. It may even
involve a smaller diameter of the centralizer device than the wall of the
bore hole. The locked state is used for deploying the casing or other
conduit longitudinally along the bore hole. The released state involves a
larger pressure between the centralizer device and the surrounding wall
of the bore hole than a traditional centralizer device, in order to
ensure centralization of the casing or other conduit. Not the least it is
important that the centralizer device, both during deployment and during
running and cementing of the casing in the bore hole, is robust and
reliable and suitable to fulfill predetermined requirements to
centralization/standoff. Transition from the locked state to the released
state may be performed according to the present disclosure by means of a
trigger mechanism.

[0012] The disclosed centralizer device involves a centralizer for
centralizing of a bore hole component in a bore hole, wherein the trigger
mechanism is configured to have a locked state and a released state. The
locked state is a state in which the trigger mechanism comprises an outer
sleeve and an inner sleeve, the inner sleeve attached to the bore hole
component. In the locked state of the centralizer device, the outer
sleeve comprising ribs and an inner sleeve are locked to each other, so
that longitudinal movements between the outer sleeve comprising ribs and
the inner sleeve are prevented, in that there is deployed a lock spring
inside an outer sleeve latch groove which also is in an inner sleeve
latch groove. In the released state of the centralizer device, the outer
sleeve comprising ribs and the inner sleeve are released from each other,
so that movements between the outer sleeve and the inner sleeve are made
possible because the lock spring is located in just one of the inner
latch groove and the outer latch groove; and ribs in the outer sleeve are
arranged to get released and attempt to increase its circumference, in
that ribs are pre-tensioned outwards as with a larger diameter than the
one in the locked state, so that the ribs push against the wall of the
bore hole having a smaller diameter than said pre-tensioned ribs and in
this way the centralizer is arranged to centre the bore hole component.

[0013] A centralizer device for centre positioning of a bore hole
component in a bore hole according to the present disclosure is arranged
to have two possible different states, one locked state and one released
state. Said centralizer device comprises one outer sleeve comprising ribs
and one inner sleeve being fastened to a bore hole component. A
pre-tensioned lock spring is provided clinging to a pre-tensioned release
spring with an opposite tension dominating the tension of the lock
spring. In the locked state of the centralizer device the outer sleeve
and the inner sleeve are locked to each other, so that longitudinal
movement between the outer sleeve the inner sleeve is prevented, in that
the lock spring is positioned both in an outer sleeve latch groove and in
an inner sleeve latch groove; and the ribs are pre-tensioned with outward
strain and the release spring being squeezed towards the inner sleeve by
a snap ribbon. In the released state of the centralizer device the outer
sleeve and the inner sleeve are released from each other so that
longitudinal movement between the outer sleeve and the inner sleeve is
made possible in that the lock spring is positioned completely in the
outer sleeve latch groove. This results in the pre-tensioned ribs
applying pressure against the wall of the bore hole; and the release
spring being released and the lock spring as a consequence is positioned
so that it is completely inside the outer sleeve latch groove. The snap
ribbon has two possible different states related to the two states of the
centralizer device, the locked and the released states. In the locked
state of the snap ribbon it comprises one or more snap-ribbon units
connected to each other. The snap-ribbon unit comprises a male snap-part,
a female snap-part and pH-soluble material, positioned between the male
snap-part and the female snap-part. pH-soluble material is material
prepared to get dissolved when subject to fluid having a pH-value within
a specified range. This arrangement locks the male snap-part and the
female snap-part together on a first end of the male snap-part and a
first end of female snap-part. The snap ribbon connected with an opposite
end of a male snap-part joined to an opposite end of a female snap-part
and deployed in the inner sleeve latch groove, has a length that results
in squeezing said release spring towards the inner sleeve resulting in
the lock spring locking the outer sleeve to the inner sleeve. In the
released state of the snap ribbon, the pH-soluble material positioned
between the male snap-part and the female snap-part has been dissolved
and said interlocking is void and said squeezing of the release spring by
the snap ribbon is void, resulting in the release spring being released.
The lock spring being pressed inside the outer sleeve, the sleeves being
released from each other enable the ribs pushing against the bore hole
wall results in centralizing the centralizing device in the bore hole.
The transition from the locked state to the released state is configured
to be initiated by subjecting the pH-soluble material to a fluid having a
pH value so as to dissolve the pH-soluble material.

[0014] In some embodiments, the fluid having a pH-value outside the range
9.0 to 9.5.

[0015] In some embodiments, the fluid having a pH-value outside the range
7.0 to 11.0.

[0016] In some embodiments, the borehole component is a casing.

[0017] In some embodiments, the borehole component is a foundation plug.

[0018] A method for deploying of a centralizer device according to the
present disclosure may comprise the following actions. One side of a
centralizer device is fastened longitudinally to a bore hole component to
deploy the bore hole component together with the centralizer device in a
bore hole. Bore fluid having a pH-value of between 7.0 and 11.0 is pumped
into the bore hole component and further into the annulus between the
bore hole component and the bore hole. A pill of bore fluid having a
pH-value outside the range of pH-values of said bore fluid is pumped into
the bore hole, initiating the centralizer device to change from its
locked state to its released state so that the bore hole component gets
centred inside the bore hole. The bore hole component may then be
cemented in place.

[0019] In some embodiments, the borehole component comprises a casing.

[0020] In some embodiments, the borehole component comprises a foundation
plug.

[0021] In some embodiments the bore fluid has a pH-value between 9.0 to
9.5.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a longitudinal perspective view of a casing with a
centralizer device around the casing, shown in its locked state.

[0023] FIG. 2 is a longitudinal perspective view of a casing with a
centralizer device around the casing, shown in its released state.

[0024] FIG. 3 is a cross section view of a casing with a centralizer
device around the casing, shown in its locked state.

[0025] FIG. 4A is a longitudinal view through a part of one side of a
centralizer in a locked state.

[0026] FIG. 4B is a longitudinal view through a part of one side of a
centralizer about to change states from locked to released.

[0027] FIG. 4C is a longitudinal view through a part of one side of a
centralizer in a released state.

[0028] FIG. 5A is a top view of a male snap-part.

[0029] FIG. 5B is a top view of a female snap-part.

[0030] FIG. 5C is a side view of the male snap-part.

[0031] FIG. 5D is a side view of a female snap-part.

[0032] FIG. 5E is a top view of a snap-ribbon unit.

[0033] FIG. 5F is a side view of the snap-ribbon unit.

[0034] FIG. 5G is a side view of a snap-ribbon with six snap-ribbon units.

[0035] Reference numbers in the drawings relate to the following elements
in the detailed description:

[0036] 10 Outer sleeve

[0037] 20 Inner sleeve

[0038] 25 Inner sleeve latch groove

[0039] 30 Snap ribbon

[0040] 31 Male snap-part

[0041] 32 Female snap-part

[0042] 35 Snap ribbon unit

[0043] 40 Set screw

[0044] 51 Lock spring

[0045] 52 Release spring

[0046] 60 pH-soluble material

[0047] 70 Outer sleeve latch groove

[0048] 90 Bore hole component

[0049] 91 Casing

[0050] 100 Centralizer device

DETAILED DESCRIPTION

[0051] In the following a centralizer device and method are described in
more detail with reference to the drawings.

[0052] One embodiment is shown in FIG. 1. When producing a well for
exploration of hydrocarbon such as oil, a bore hole is bored into the
formation in which it is assumed that there are deposits of hydrocarbon.
Thereafter, segments of casing 91 are inserted after one another into the
bore hole with so called centralizer devices 100 assembled on the outside
of the casing segments. The centralizer devices 100 are assembled on the
casing 91 with some distance between them, as mentioned previously. In
deep bore holes and in particular at instances where the bore hole is
curved and maybe continues sloping or in horizontal direction, frictions
forces that operate against deploying forces when using conventional
centralizer devices will make it all the more demanding to deploy the
casing 91.

[0053] The centralizer device 100 is arranged around the casing 91 during
deployment of the casing 91 in a bore hole and is to center the casing at
suitable distances. In the present embodiment, the centralizer device 100
is configured to having two possible states. In the locked state, the
casing 91, comprising one or more centralizer devices 100, all in their
locked state but inside the bore hole, less force is pushing the ribs
against the wall of the bore hole. Its diameter may even be smaller than
the diameter of the borehole in the locked state of the centralizing
device. The casing 91 will therefore experience less friction against the
wall of the bore hole than with a conventional centralizer device which
presses with greater force against a wall of a bore hole.

[0054] In FIG. 1, the centralizer device 100 is presented in its locked,
not released, state called the "locked state." The centralizer device 100
has an inner sleeve 20 that is positioned proximate to the casing 91. The
inner sleeve 20 is attached to the casing 91 so that the inner sleeve 20
is arranged to prevent movement of the inner sleeve 20 along the casing
91. This attachment can be accomplished by e.g. utilizing one or more set
screws 40 through the inner sleeve 20 and towards the casing 91. An outer
sleeve 10 with ribs is positioned immediately on the outside of the inner
sleeve 20. The ribs on this are in the locked state pre-tensioned so that
the outer sleeve 10 with ribs, when not inserted into a well, has a
smaller diameter as compared with in the released state. One longitudinal
end of the outer sleeve extends longer than the inner sleeve 20 and
constitutes an edge in that the outer sleeve 10 with ribs has an inner
diameter that is less than the outer diameter of the inner sleeve 20 in
this end. The outer sleeve 10 rests with this edge against the end of the
inner sleeve 20 and the outer sleeve 10 is in the locked state
pre-tensioned in that its second end in the longitudinal direction is
stretched so that an inner sleeve latch groove 25 is positioned opposite
an outer sleeve latch groove 70. The outer sleeve 10 is locked in this
locked state because there is one lock spring 51 positioned in both the
inner sleeve latch groove 25 and in the outer sleeve latch groove 70.

[0055] In FIG. 1, the centralizer device 100 is shown in the locked state.
The ribs of the outer sleeve 10 are pre-tensioned with outward strain.
The outer sleeve 10 is fixed to the borehole component 90, 91 e.g. with a
set screw 40 or otherwise. The outer sleeve 10 is fastened proximate one
longitudinal end to the inner sleeve 20. In order to stay in this locked
state, a locking mechanism is arranged.

[0056] FIG. 2 is a longitudinal perspective view of a casing 91 with a
centralizer device 100 around the casing, shown in its released state.

[0057] FIG. 3 is a cross section view of a casing with a centralizer
device around the casing, shown in its locked state.

[0058] In FIG. 4A, a lock spring 51 is positioned both in the outer sleeve
latch groove 70 and in an inner sleeve latch groove (25 in FIG. 4C) in an
opposite longitudinal end of the inner sleeve 20. With this locking
mechanism, the outer sleeve 10 is prevented from releasing the
pre-tension of its ribs, thereby the centralizer device 100 and the lock
spring 51 stay in this locked state.

[0059] The present locking mechanism, using a lock ring to prevent and
enable longitudinal movement between two sleeves may be used together
with not only the present embodiment of a centralizer device 100, but to
other ways of triggering, e.g. rubber swelling when exposed to
pH-variations, electrical triggering, triggering by elevated temperature
in the well bore over some length of time. The locking mechanism can also
be used with arrangements with modified details of the present
disclosure.

[0060] Said lock spring 51 is pre-tensioned so that it clings to a release
spring 52. Said release spring 52 is pre-tensioned the opposite way so
that the lock spring 51 clings to the release spring 52.

[0061] In FIG. 4B, the release spring 52 is shown in transition between
the locked state and a released state of the centralizer device 100 and
the lock spring 51. The lock spring 51, still clinging to the release
spring 52, is moved generally in its entirety into the outer sleeve latch
groove 70. The pre-tension of the ribs of the outer sleeve 10 results in
a longitudinal force tending to move the outer sleeve 10 along the inner
sleeve 20. With the lock spring 51 now inside the outer sleeve latch
groove 70, the outer sleeve 10 will move as indicated. The lock spring 51
will then slide on the outside of the inner sleeve 20.

[0062] The release spring 52 is kept in a locked state by a snap ribbon
30, also in a locked state, positioned outside and around said release
spring 52. The snap ribbon 30 squeezes the release spring 52 toward the
inner sleeve 20.

[0063] FIG. 4C shows the locking mechanism in the released position,
wherein the release spring 52 is no longer restrained by the lock spring
51.

[0064] The snap ribbon 30 comprises at least one snap ribbon unit (35 in
FIG. 5G) connected back to back to itself or one snap ribbon unit (35 in
FIG. 5G) to another one as indicated in FIG. 5G. In FIG. 5G there are 6
snap ribbon units 35, but the minimum snap ribbon units 35 in a snap
ribbon is 1.

[0066] A male snap-part 31 is presented in FIGS. 5A seen from above and in
FIG. 5C seen in side view. A female snap-part 32 is presented in FIGS. 5B
seen from above and FIG.

[0067] 5D seen in side view. FIG. 5E indicates in top view how a male
snap-part 31 and a female snap-part 32 can be assembled. FIG. 5F
indicates this in side view and in this figure, a piece of pH-soluble
material 60 is also inserted which locks the male snap-part 31 and the
female snap-part 32 together. The snap ribbon unit 35 then is in a locked
state.

[0068] FIG. 5G presents the snap ribbon 30 with six snap ribbon units 35
all in locked state resulting in the snap ribbon itself being in a locked
state.

[0069] With all components of the centralizer device 100 assembled and in
the locked state, the centralizer device 100 may be entered around a
borehole component 90, 91 as described above. Then the centralizer device
100 and the borehole component 90, 91 may be inserted into the borehole.
They are, as persons in the art will understand, inserted one after
another. The distance between the centralizer devices may vary depending
on conditions e.g. angle of deployment of the bore hole component 90, 91.
One deployed borehole component 90, 91 may carry none, one or more than
one centralizer device 100.

[0070] When the bore hole components 90, 91 including centralizer devices
100 are deployed in the borehole, a pill with a pH-value that makes
pH-soluble material 60 in the snap ribbon units 35 of the snap ribbons 30
of the centralizer devices 100 dissolve is inserted in a flow of drill
fluid. This results in the pH-material 60 dissolving and then a snap
ribbon unit 35, the snap ribbon 30, the release spring 52, the lock
spring 51 and the outer sleeve 10 comprising ribs, leaving their locked
state and entering the released state. In other words, it makes the
centralizer devices 100 leave the locked state and enter the released
state. In the released state the centralizer devices 100 push their ribs
against the wall of the bore hole and centralizes the bore hole component
90, 91. Afterwards, cement may be pumped inside the bore hole component
90, 91 and further to the annulus between the bore hole component 90, 91
and the wall of the bore hole.

[0071] All the time before cement fixes the bore hole component 90, 91,
the bore hole component 90, 91 may freely be rotated, both when the
centralizer 100 is in its locked state and when in its released state.

[0072] A centralizer device 100 in the locked state and deployed in a bore
hole with a drill fluid as described in the above paragraph will stay in
its locked state.

[0073] A so called drill fluid pill may be added to drill fluid in order
to modify properties of the drill fluid. A drill fluid pill arranged to
modify the pH-value in the used drill fluid by e.g. plus 2, e.g. from a
pH-value in the range of 9.0 to 9.5 to a pH-value of between 11.0 and
11.5. Further on, the centralizer device 100 is arranged so that it in an
environment of drill fluid of at least 11.0 moves from the locked state
to the released state. The locked state will get the permanent one that
the centralizer device stays in, even if the pH-value drops to less than
11.0 again after that the centralizer device 100 has entered the released
state.

[0074] In another embodiment, a drill fluid pill arranged to modify the
pH-value in the drill fluid in question by minus 2 may be added to the
drill fluid, e.g. from a pH-value in the range of 9.0 to 9.5 to a
pH-value of between 7.0 and 7.5. The centralizer device 100 is further on
arranged so that in an environment of drill fluid having a pH-value of
less than 7.5 the device 100 transforms from its locked state to its
released state. The centralizer device 100 will remain in the released
state, even if the pH-value subsequently increases to more than 7.5 after
that the centralizer device 100 has entered the released state.

[0075] In another embodiment, a drill fluid pill arranged to modify the
pH-value in the drill fluid in question by plus 3 may be added to the
drill fluid, e.g. from a pH-value in the range of 7.0 to 10.0 to a
pH-value of between 10.0 and 13.0. The centralizer device 100 is further
on arranged so that it in an environment of drill fluid having a pH-value
of at least 13.0 transforms from its locked state to its released state.
The centralizer deice 100 will stay permanently in the released state,
even if the pH-value subsequently changes to less than 10.0 again after
that the centralizer device 100 has arrived at its released state.

[0076] In another embodiment, a drill fluid pill arranged to modify the
pH-value in the drill fluid in question by minus 3 may be added to the
drill fluid, e.g. from a pH-value in the range of 7.0 to 10.0 to a
pH-value of between 4.0 and 7.0. The centralizer device 100 is further on
arranged so that it in an environment of drill fluid having a pH-value of
less than 7.0 transforms from its locked state to its released state. The
centralizer device 100 will stay permanently in the released state, even
if the pH-value subsequently increases to more than 7.0 after that the
centralizer device 100 has arrived at its released state.

[0077] In other embodiments, a method and centralizer device according to
the present disclosure may be used to center a mechanical plug (not shown
in the drawings) that is to operate as a foundation for establishing a
concrete plug (not shown in the drawings), a so called foundation plug.
Such a foundation plug with a cement plug on top can be used for
different operation purposes: [0078] 1. Drilling of side step. In this
embodiment, the foundation plug and the cement plug constitute a ramp
resulting in drilling that follows is guided away from the present well
track and in a preferred angle from this. [0079] 2. Sealing of a problem
zone. In this embodiment, the foundation plug and the cement plug are
used to seal off a problem zone e.g. comprising gas that one have drilled
into. [0080] 3. Preventing cross flow of hydro carbons. In this
embodiment, the foundation plug and the cement plug are used to prevent
cross flow of hydro carbons in a reservoir.

[0081] Drill fluid may be oil based or water based. The methods and
apparatus according to the present disclosure can be used with both
types. One example of the former is Versatec OBM (Oil Based Mud) that may
have a pH-value of between 9.0 and 9.5. An example of the second type,
WBM (Water Based Mud) is Glydril that may have a pH-value of between 7.0
and 9.0.

[0082] Those versed in the art will recognize that the pH-limit values of
both drill fluid, pH-soluble material (60 in FIG. 5F) and drill fluid
pills may vary within wide boundaries. In order for a centralizing device
according to the present disclosure to operate according to its purpose,
these values may be chosen based upon practical reasoning so as to ensure
that the centralizer device 100 is not released from its locked state
with the chosen drill fluid, but is arranged to be released and arrive in
its released state when the pH-soluble material contacts the chosen drill
fluid pill.

[0083] In the present disclosure, the terms drill fluid and mud are
intended to mean the same thing. pH-soluble material (60) that has
dissolved is in the present document regarded as equivalent to being
void.

[0084] Although only a few examples have been described in detail above,
those skilled in the art will readily appreciate that many modifications
are possible in the examples. Accordingly, all such modifications are
intended to be included within the scope of this disclosure as defined in
the following claims. In the claims, means-plus-function clauses are
intended to cover the structures described herein as performing the
recited function and not only structural equivalents, but also equivalent
structures. Thus, although a nail and a screw may not be structural
equivalents in that a nail employs a cylindrical surface to secure wooden
parts together, whereas a screw employs a helical surface, in the
environment of fastening wooden parts, a nail and a screw may be
equivalent structures. It is the express intention of the applicant not
to invoke 35 U.S.C. .sctn.112(f), for any limitations of any of the
claims herein, except for those in which the claim expressly uses the
words "means for" together with an associated function.